Washington — Since taking office three-plus years ago, President Obama has walked a fine line on race. “I’m the president of the entire United States,” he has said, when asked by black activists and reporters why he’s not doing more to help struggling African-Americans.

But there are times when the nation's first black president “goes there” on race, as when he reacted to the recent killing of unarmed black teen Trayvon Martin. “If I had a son, he’d look like Trayvon,” Mr. Obama memorably said – a comment that sparked fierce debate over whether the president was using the case for political ends.

On Thursday night, the theme of racial discrimination in America comes to the White House Family Theater, as Obama introduces a screening of the Academy Award-winning film “To Kill a Mockingbird,” in honor of its 50th anniversary. And with the president perhaps cast as “teacher in chief,” the White House has invited schoolchildren from the area to attend. The film, based on the Pulitzer Prize-winning book by Harper Lee, tells the story of a white Southern lawyer, Atticus Finch, who defends a black man, Tom Robinson, wrongly accused of rape.

“I’m deeply honored that President Obama will be celebrating the 50th Anniversary of ‘To Kill a Mockingbird’ by introducing it to a national audience,” the reclusive Ms. Lee said in a statement released by USA, Universal Pictures, and the American Film Institute (AFI). “I believe it remains the best translation of a book to film ever made, and I'm proud to know that Gregory Peck's portrayal of Atticus Finch lives on – in a world that needs him now more than ever.”

According to The Hollywood Reporter, other notable people will be in the audience Thursday night: Mary Badham, who played Mr. Finch’s daughter, Scout, in the movie; Veronique Peck, widow of Mr. Peck; Howard Stringer, chairman of the AFI board of trustees; Ron Meyer, president and COO of Universal Studios; Bob Gazzale, AFI president and CEO; and Arne Duncan, secretary of Education.

As president, Obama’s path on racial matters has been filled with land mines. In the summer of 2009, his response to a reporter’s question on the arrest of black scholar Henry Louis Gates Jr. by a white police officer produced weeks of uproar. Obama said the Cambridge, Mass., police had acted “stupidly,” stepping on the preceding 55 minutes of a news conference devoted to his plan for health-care reform.

Obama said he hoped the episode would produce a “teachable moment,” but it’s not clear that the “beer summit” he held with Professor Gates, Sgt. James Crowley, and Vice President Joe Biden to smooth things over taught the nation anything more than that race remains a fraught subject.

On the Trayvon Martin case, Obama was under pressure from leading African-Americans to speak out long before he did. Trayvon was shot to death by neighborhood watch volunteer George Zimmerman in Sanford, Fla., in late February. Obama didn’t make his comment until March 23. Black commentators praised the statement as pitch perfect. But Obama faced a backlash from some conservatives, who accused African-Americans of playing the race card to boost Obama’s reelection chances.

"Rather than holding rallies on these issues, the civil rights leadership focuses on racially polarizing cases to generate media attention and to mobilize black voter turnout," Richard Land, president of the Southern Baptist Convention's Ethics & Religious Liberty Commission, said on his radio program last weekend, according to the Religion News Service.

The Trayvon Martin case has led Reniqua Allen of the New America Foundation to a stark conclusion: that the first black president has made it harder to talk about race in America.

In an essay in The Washington Post, she noted her optimism after Obama stated on March 23, “All of us have to do some soul-searching to figure out: How does something like this happen?”

“It’s an important conversation to have – but I fear it won’t lead anywhere,” Ms. Allen wrote. "After all, we’ve seen plenty of these debates in recent years, invariably prompted by some tragedy or controversy. Think Troy Davis. Or Shirley Sherrod. Or Jeremiah Wright. Or Henry Louis Gates Jr. Or even Rodney King. We have big debates over racial prejudice and disparities in this country, and then nothing happens.”

“I thought things would be different by now,” Allen continued. “The Trayvon Martin story flared up exactly four years after Obama’s famous campaign speech on race in Philadelphia, a speech that made so many of us believe that Obama would launch a serious, enduring dialogue. But the election of the first black president hasn’t made it easier to talk about race in America. It’s made it harder.”